Sorry, I am not aware, how to do it. If you are strong in dojox.gfx, you could probably do it, by getting the dojoShape and manipulating it and updating the shape back to geometry, like earlier. But I cannot confirm it.

If the users does not need it, I would suggest you to disable the scaling. It would be easier if you were using EditToolbar instead of Editor Widget. The way to do it here.